DESCRIPTION

The stack KPI allows querying of kernel stack trace information and the
automated generation of kernel stack trace strings for the purposes of
debugging and tracing. stack relies on the presence of DDB(4), and all
use of these functions must be made conditional on DDB being compiled in
the kernel.
Each stack trace is described by a structstack. Before a trace may be
created or otherwise manipulated, storage for the trace must be allocated
with stack_create(), which may sleep. Memory associated with a trace may
be freed by calling stack_destroy().
A trace of the current kernel thread’s call stack may be captured using
stack_save().
stack_print() may be used to print a stack trace using the kernel
printf(9).
stack_sbuf_print() may be used to construct a human-readable string,
including conversion (where possible) from a simple kernel instruction
pointer to a named symbol and offset. The argument sb must be an
initialized struct sbuf as described in sbuf(9). This function may sleep
if an auto-extending struct sbuf is used.
The utility functions stack_zero, stack_copy, and stack_put may be used
to manipulate stack data structures directly.